Development and long‐term stability of a comprehensive daily QA program for a modern pencil beam scanning (PBS) proton therapy delivery system

Purpose The main purpose of this study is to demonstrate the clinical implementation of a comprehensive pencil beam scanning (PBS) daily quality assurance (QA) program involving a number of novel QA devices including the Sphinx/Lynx/parallel‐plate (PPC05) ion chamber and HexaCheck/multiple imaging modality isocentricity (MIMI) imaging phantoms. Additionally, the study highlights the importance of testing the connectivity among oncology information system (OIS), beam delivery/imaging systems, and patient position system at a proton center with multi‐vendor equipment and software. Methods For dosimetry, a daily QA plan with spot map of four different energies (106, 145, 172, and 221 MeV) is delivered on the delivery system through the OIS. The delivery assesses the dose output, field homogeneity, beam coincidence, beam energy, width, distal‐fall‐off (DFO), and spot characteristics — for example, position, size, and skewness. As a part of mechanical and imaging QA, a treatment plan with the MIMI phantom serving as the patient is transferred from OIS to imaging system. The HexaCheck/MIMI phantoms are used to assess daily laser accuracy, imaging isocenter accuracy, image registration accuracy, and six‐dimensional (6D) positional correction accuracy for the kV imaging system and robotic couch. Results The daily QA results presented herein are based on 202 daily sets of measurements over a period of 10 months. Total time to perform daily QA tasks at our center is under 30 min. The relative difference (Δrel) of daily measurements with respect to baseline was within ± 1% for field homogeneity, ±0.5 mm for range, width and DFO, ±1 mm for spots positions, ±10% for in‐air spot sigma, ±0.5 spot skewness, and ±1 mm for beam coincidence (except 1 case: Δrel = 1.3 mm). The average Δrel in dose output was −0.2% (range: −1.1% to 1.5%). For 6D IGRT QA, the average absolute difference (Δabs) was ≤0.6 ± 0.4 mm for translational and ≤0.5° for rotational shifts. Conclusion The use of novel QA devices such as the Sphinx in conjunction with the Lynx, PPC05 ion chamber, HexaCheck/MIMI phantoms, and myQA software was shown to provide a comprehensive and efficient method for performing daily QA of a number of system parameters for a modern proton PBS‐dedicated treatment delivery unit

An evaluation of the stability of image quality parameters of Varian on-board imaging (OBI) and EPID imaging systems

Purpose: Quality assurance of the image quality for image guided localization systems is crucial to ensure accurate visualization and localization of target volumes. In this study, the stability of selected image parameters was assessed and evaluated for CBCT mode, planar radiographic kV mode and the radiographic MV EPID mode.Methods and Materials: The CATPHAN, QckV-1 and QC-3 phantoms were used to evaluate the image quality parameters. The planar radiographic images were analyzed in PIPSpro™ with spatial resolution (f30, f40, f50) being recorded. For OBI CBCT, High quality head Full-Fan acquisition and Pelvis Half-Fan acquisition modes were evaluated for Uniformity, Noise, Spatial Resolution, HU constancy and geometric distortion. Dose and kVp for the OBI were recorded using the Unfors RaySafe Xi system with the R/F High Detector for planar kV and the CT detector for CBCT. Dose for the MV EPID was recorded using a PTW975 Semiflex Ion Chamber, webline electrometer and 1cm SolidWater™.Results: For each metric, values were normalized to the mean and the standard deviations were recorded. Table 1 shows the standard deviation for all results. Using this, tolerances can be reported as a warning threshold of 1σ and an action threshold of 2σ. Table 2 shows the warning and action tolerances for the planar radiographic modalities while Table 3 and 4 show tolerance levels for the Full-Fan and Half-Fan, respectively.Conclusion: A study was performed to assess the stability of the basic image quality parameters recommended by TG-142 for the Varian OBI and EPID Imaging systems. The two systems show consistent imaging and dosimetric properties over the evaluated time frame.----------------------------Cite this article as: Stanley DN, Papanikolaou N, Gutierrez AN. An evaluation of the stability of image quality parameters of Varian on-board imaging (OBI) and EPID imaging systems. Int J Cancer Ther Oncol 2014; 2(2):020236. DOI: 10.14319/ijcto.0202.3

An evaluation of the stability of image quality parameters of Varian on-board imaging (OBI) and EPID imaging systems

Purpose: Quality assurance of the image quality for image guided localization systems is crucial to ensure accurate visualization and localization of target volumes. In this study, the stability of selected image parameters was assessed and evaluated for CBCT mode, planar radiographic kV mode and the radiographic MV EPID mode.Methods and Materials: The CATPHAN, QckV-1 and QC-3 phantoms were used to evaluate the image quality parameters. The planar radiographic images were analyzed in PIPSpro™ with spatial resolution (f30, f40, f50) being recorded. For OBI CBCT, High quality head Full-Fan acquisition and Pelvis Half-Fan acquisition modes were evaluated for Uniformity, Noise, Spatial Resolution, HU constancy and geometric distortion. Dose and kVp for the OBI were recorded using the Unfors RaySafe Xi system with the R/F High Detector for planar kV and the CT detector for CBCT. Dose for the MV EPID was recorded using a PTW975 Semiflex Ion Chamber, webline electrometer and 1cm SolidWater™.Results: For each metric, values were normalized to the mean and the standard deviations were recorded. Table 1 shows the standard deviation for all results. Using this, tolerances can be reported as a warning threshold of 1σ and an action threshold of 2σ. Table 2 shows the warning and action tolerances for the planar radiographic modalities while Table 3 and 4 show tolerance levels for the Full-Fan and Half-Fan, respectively.Conclusion: A study was performed to assess the stability of the basic image quality parameters recommended by TG-142 for the Varian OBI and EPID Imaging systems. The two systems show consistent imaging and dosimetric properties over the evaluated time frame.----------------------------Cite this article as: Stanley DN, Papanikolaou N, Gutierrez AN. An evaluation of the stability of image quality parameters of Varian on-board imaging (OBI) and EPID imaging systems. Int J Cancer Ther Oncol 2014; 2(2):020236. DOI: 10.14319/ijcto.0202.36</p

Comparison of low contrast sensitivity among multi-slice CT units using various mAs setting for the potential benefit of non-MRI compatible, stereotactic radiosurgery (SRS) patients

Purpose: To evaluate the low contrast detectability sensitivity among 4-slice, 8-slice and 16-slice CT units using various mAs settings. Findings of the study may elucidate the most optimal imaging parameter for stereotactic radiosurgery (SRS) patients who are not MRI compatible.Methods and Materials: Low contrast targets in the CATPHAN phantom (model: CTP 504, The Phantom Laboratory) were imaged on a 4-slice LightSpeed Advantage™ GE CT scanner (GE Healthcare, WI) and a 16- slice LightSpeed Advantage™ GE CT scanner (GE Healthcare, WI) in 8-slice and 16-slice mode. The CATPHAN CTP515 low contrast targets of size 15, 9, 8, 7, 6, 5, 4, 3 and 2 mm for each contrast difference of 1%, 0.5% and 0.3% from the water-equivalent background was imaged using a SRS protocol. Two image sets per setting were acquired for mAs parameters of 300, 350 and 440. Images were evaluated in a blind study by three independent reviewers.Results: Using 300,350 and 440mAs settings on the 4-slice scanner, the average smallest diameters recorded at 1% contrast were 5 ± 1 mm, 5 ± 1 mm and 5 ± 0 mm and at 0.5% were 7 ± 2 mm, 7 ± 1 mm and 6 ± 1 mm. For the 8 - slice scanner, the average smallest diameters recorded at 1% contrast were 7 ± 0 mm, 6 ± 0 mm and 5 ± 0 mm, and at 0.5% were 12 ± 3 mm, 9 ± 1 mm and 6 ± 1 mm. For the 16 - slice scanner, the average smallest diameters recorded at 1% contrast were 7 ± 1 mm, 7 ± 1 mm and 6 ± 1 mm, and at 0.5% were 11 ± 3 mm, 8 ± 1 mm and 8 ± 1 mm. A difference was observed between the 4 and 8 - slice scanners at 300mAs (p &lt; 0.01) for each contrast level as well as the 4 and 16 slice at 440 (p &lt; 0.01) and 350 (p &lt; 0.01) mAs. Additionally, a difference was observed between each mAs for the 8 slice at 1% (p &lt; 0.01) and 0.5% (p &lt; 0.01) contrast.Conclusion: Results demonstrate consistently improved low contrast detectability as mAs was increased. CT simulation imaging parameters can be optimized to improve low contrast sensitivity for non MRI compatible SRS patients.----------------Cite this article as: Stanley D, Narayanasamy G, Breton C, Papanikolaou N, Gutierrez AN. Comparison of low contrast sensitivity among multi-slice CT units using various mAs setting for the potential benefit of non-MRI compatible, stereotactic radiosurgery (SRS) patients. Int J Cancer Ther Oncol 2014; 2(2):020237. DOI: 10.14319/ijcto.0202.37</p

Comparison of low contrast sensitivity among multi-slice CT units using various mAs setting for the potential benefit of non-MRI compatible, stereotactic radiosurgery (SRS) patients

Purpose: To evaluate the low contrast detectability sensitivity among 4-slice, 8-slice and 16-slice CT units using various mAs settings. Findings of the study may elucidate the most optimal imaging parameter for stereotactic radiosurgery (SRS) patients who are not MRI compatible.Methods and Materials: Low contrast targets in the CATPHAN phantom (model: CTP 504, The Phantom Laboratory) were imaged on a 4-slice LightSpeed Advantage™ GE CT scanner (GE Healthcare, WI) and a 16- slice LightSpeed Advantage™ GE CT scanner (GE Healthcare, WI) in 8-slice and 16-slice mode. The CATPHAN CTP515 low contrast targets of size 15, 9, 8, 7, 6, 5, 4, 3 and 2 mm for each contrast difference of 1%, 0.5% and 0.3% from the water-equivalent background was imaged using a SRS protocol. Two image sets per setting were acquired for mAs parameters of 300, 350 and 440. Images were evaluated in a blind study by three independent reviewers.Results: Using 300,350 and 440mAs settings on the 4-slice scanner, the average smallest diameters recorded at 1% contrast were 5 ± 1 mm, 5 ± 1 mm and 5 ± 0 mm and at 0.5% were 7 ± 2 mm, 7 ± 1 mm and 6 ± 1 mm. For the 8 - slice scanner, the average smallest diameters recorded at 1% contrast were 7 ± 0 mm, 6 ± 0 mm and 5 ± 0 mm, and at 0.5% were 12 ± 3 mm, 9 ± 1 mm and 6 ± 1 mm. For the 16 - slice scanner, the average smallest diameters recorded at 1% contrast were 7 ± 1 mm, 7 ± 1 mm and 6 ± 1 mm, and at 0.5% were 11 ± 3 mm, 8 ± 1 mm and 8 ± 1 mm. A difference was observed between the 4 and 8 - slice scanners at 300mAs (p &lt; 0.01) for each contrast level as well as the 4 and 16 slice at 440 (p &lt; 0.01) and 350 (p &lt; 0.01) mAs. Additionally, a difference was observed between each mAs for the 8 slice at 1% (p &lt; 0.01) and 0.5% (p &lt; 0.01) contrast.Conclusion: Results demonstrate consistently improved low contrast detectability as mAs was increased. CT simulation imaging parameters can be optimized to improve low contrast sensitivity for non MRI compatible SRS patients.----------------Cite this article as: Stanley D, Narayanasamy G, Breton C, Papanikolaou N, Gutierrez AN. Comparison of low contrast sensitivity among multi-slice CT units using various mAs setting for the potential benefit of non-MRI compatible, stereotactic radiosurgery (SRS) patients. Int J Cancer Ther Oncol 2014; 2(2):020237. DOI: 10.14319/ijcto.0202.3

Mathematical analysis of approximate biological effective dose (BED) calculation for multi-phase radiotherapy treatment plans

Purpose: There is growing interest about biological effective dose (BED) and its application in treatment plan evaluation due to its stronger correlation with treatment outcome. An approximate biological effective dose (BEDA) equation was introduced in order to simplify BED calculations by treatment planning systems in multi-phase treatments. The purpose of this work is to reveal its mathematical properties relative to the true, multi-phase BED (BEDT) equation.Methods: The BEDT equation was derived and used to reveal the mathematical properties of BEDA. MATLAB (MathWorks, Natick, MA) was used to simulate and analyze common and extreme clinical multi-phase cases. In those cases, percent error and Bland-Altman analysis were used to study the significance of the inaccuracies of BEDA for different combinations of total doses, numbers of fractions, doses per fractions and α/β values. All the calculations were performed on a voxel-basis in order to study how dose distributions would affect the accuracy of BEDA.Results: When the voxel dose-per-fractions (DPF) delivered by both phases are equal, BEDA and BEDT are equal (0% error). In heterogeneous dose distributions, which significantly vary between the phases, there are fewer occurrences of equal DPFs and hence the imprecision of BEDA is greater. It was shown that as the α/β ratio increased the accuracy of BEDA would improve. Examining twenty-four cases, it was shown that the range of DPF ratios for 3% Perror varied from 0.32 to 7.50Gy, whereas for Perror of 1% the range varied from 0.50 to 2.96Gy.Conclusion: The DPF between the different phases should be equal in order to render BEDA accurate. OARs typically receive heterogeneous dose distributions hence the probability of equal DPFs is low. Consequently, the BEDA equation should only be used for targets or OARs that receive uniform or very similar dose distributions by the different treatment phases.---------------------------Cite this article as: Kauweloa KI, Gutierrez AN, Bergamo A, Stathakis S, Papaniko-laou N, Mavroidis P. Mathematical analysis of approximate biological effective dose (BED) calculation for multi-phase radiotherapy treatment plans. Int J Cancer Ther Oncol 2014; 2(2):020226. DOI: 10.14319/ijcto.0202.2

Pregnant women's perspectives about maternal immunization in Latin America

Background: Maternal immunization rates and vaccine uptake in Latin America vary from country to country. This variability stems from factors related to pregnant women, vaccine recommendations from healthcare providers and the health system. The aim of this paper is to describe women's knowledge and attitudes to maternal immunziation, and barriers to access and vaccination related decision-making processes in Latin American countries. Methods: We conducted focus group discussions (FGD) with pregnant women in five middle-income countries: Argentina, Brazil, Honduras, Mexico and Peru, between July 2016 and July 2018. The FGDs were conducted by trained qualitative researchers in diverse clinics located in the capital cities of these countries. Results: A total of 162 pregnant women participated in the FGDs. In general, participants were aware of the recommendation to receive vaccines during pregnancy but lacked knowledge regarding the diseases prevented by these vaccines. Pregnant women expressed a desire for clearer and more detailed communication on maternal vaccines by their healthcare professionals instead of relying on other sources of information such as the internet. Overall, participants had positive attitudes towards maternal immunization and were open to receiving vaccines in pregnancy based on general trust they have in recommendations made by their healthcare providers. The main obstacles pregnant women said they encounter were mainly centered around their clinical experience: long waiting times, vaccine shortages, and impolite behavior of healthcare providers or clinical staff. Conclusion: Important advances have been made in Latin America to promote maternal immunization. Results from this study show that an important aspect that remains to be addressed, and is crucial in improving vaccine uptake in pregnancy, is women's clinical experience. We recommend pregnant women to be treated as a priority population for providing immunization and related healthcare education. It is imperative to train healthcare providers in health communication so they can effectively communicate with pregnant women regarding maternal vaccines and can fill knowledge gaps that otherwise might be covered by unreliable sources dispensing inaccurate information.Fil: Fauzia Malik, A.. University of Yale. School of Medicine; Estados UnidosFil: Belizan, María. Instituto de Efectividad Clínica y Sanitaria; ArgentinaFil: Gutierrez, Mariana. University of Emory; Estados UnidosFil: Vilajeliu, Alba. Pan American Health Organization; Estados UnidosFil: Sanclemente, Lauren N.. University of Emory; Estados UnidosFil: Gonzalez Casanova, Ines. Indiana University; Estados Unidos. University of Emory; Estados UnidosFil: Jones, Daniel Eduardo. Instituto de Efectividad Clínica y Sanitaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Omer, Saad. University of Yale; Estados Unidos. University of Yale. School of Medicine; Estados UnidosFil: Maria Ropero, Alba. Pan American Health Organization; Estados UnidosFil: Alonso, Juan Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Efectividad Clínica y Sanitaria; Argentin

Health care providers perspectives about maternal immunization in Latin America

Background: Antenatal care providers have a key role in providing appropriate information and immunization recommendations to improve pregnant women's vaccine uptake. The objective of this study is to describe health care providers' perspectives and experience regarding the implementation of maternal immunization programs in Latin America. Methods: We conducted 33 in-depth interviews of health care providers from Argentina, Brazil, Honduras, Mexico, and Peru (6–7 per country). Qualitative data analysis was conducted using a combination of both manual techniques and the computer software program NVivo. We identified and coded main themes related to maternal immunization. Results: The main themes identified in this analysis were practices related to maternal immunization, knowledge and training, resource availability and interactions with pregnant women. Healthcare providers knew that recommendations exists but some did not know their content; they expressed concerns about insufficient training. Providers from all five countries expressed the need for additional human resources and supplies. They also expressed a desire for women to be more proactive and ask more questions during the health visits. Conclusion: This is the first multi-country study assessing the perspectives of health care providers about maternal immunization practices at the facility level in Latin America. Recommendations based on the results from this study include implementing additional trainings around maternal immunization, especially targeting obstetricians and midwives. These trainings should be conducted in coordination with improvements to supply chain and other structural issues.Fil: Malik, Fauzia A.. University of Yale; Estados UnidosFil: Alonso, Juan Pedro. Instituto de Efectividad Clínica y Sanitaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sanclemente, Lauren N.. University of Emory; Estados UnidosFil: Vilajeliu, Alba. Organización Panamericana de la Salud; Estados UnidosFil: Gutierrez, Mariana. University of Emory; Estados UnidosFil: Gonzalez Casanova, Ines. University of Emory; Estados Unidos. Indiana University; Estados UnidosFil: Jones, Daniel Eduardo. Instituto de Efectividad Clínica y Sanitaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Omer, Saad. University of Yale; Estados UnidosFil: Ropero, Alba-Maria. Organización Panamericana de la Salud; Estados UnidosFil: Belizán, María Melina Eleonora. Instituto de Efectividad Clínica y Sanitaria; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Phenotypic, transcriptomic, and genomic features of clonal plasma cells in light-chain amyloidosis

Immunoglobulin light-chain amyloidosis (AL) and multiple myeloma (MM) are 2 distinct monoclonal gammopathies that involve the same cellular compartment: clonal plasma cells (PCs). Despite the fact that knowledge about MM PC biology has significantly increased in the last decade, the same does not apply for AL. Here, we used an integrative phenotypic, molecular, and genomic approach to study clonal PCs from 24 newly diagnosed patients with AL. Through principal-component-analysis, we demonstrated highly overlapping phenotypic profiles between AL and both monoclonal gammopathy of undetermined significance and MM PCs. However, in contrast to MM, highly purified fluorescence-activated cell-sorted clonal PCs from AL (n = 9) showed almost normal transcriptome, with only 38 deregulated genes vs normal PCs; these included a few tumor-suppressor (CDH1, RCAN) and proapoptotic (GLIPR1, FAS) genes. Notwithstanding, clonal PCs in AL (n=11) were genomically unstable, with a median of 9 copy number alterations (CNAs) per case, many of such CNAs being similar to those found in MM. Whole-exome sequencing (WES) performed in 5 AL patients revealed a median of 15 nonrecurrent mutations per case. Altogether, our results show that in the absence of a unifying mutation by WES, clonal PCs in AL display phenotypic and CNA profiles similar to MM, but their transcriptome is remarkably similar to that of normal PCs

LYACOLORE: synthetic datasets for current and future Lyman-alpha forest BAO surveys

The statistical power of Lyman-α forest Baryon Acoustic Oscillation (BAO) measurements is set to increase significantly in the coming years as new instruments such as the Dark Energy Spectroscopic Instrument deliver progressively more constraining data. Generating mock datasets for such measurements will be important for validating analysis pipelines and evaluating the effects of systematics. With such studies in mind, we present LyaCoLoRe: a package for producing synthetic Lyman-α forest survey datasets for BAO analyses. LyaCoLoRe transforms initial Gaussian random field skewers into skewers of transmitted flux fraction via a number of fast approximations. In this work we explain the methods of producing mock datasets used in LyaCoLoRe, and then measure correlation functions on a suite of realisations of such data. We demonstrate that we are able to recover the correct BAO signal, as well as large-scale bias parameters similar to literature values. Finally, we briefly describe methods to add further astrophysical effects to our skewers—high column density systems and metal absorbers—which act as potential complications for BAO analyses